Enhanced control efficacy of Bacillus subtilis NM4 via integration of chlorothalonil on potato early blight caused by Alternaria solani.

Early blight caused by Alternaria solani is a common foliar disease of potato around the world, and serious infections result in reduced yields and marketability due to infected tubers. The major aim of this study is to figure out the synergistic effect between microorganism and fungicides and to evaluate the effectiveness of Bacillus subtilis NM4 in the control of early blight in potato. Based on its colonial morphology and a 16S rRNA analysis, a bacterial antagonist isolated from kimchi was identified as B. subtilis NM4 and it has strong antifungal and anti-oomycete activity against several phytopathogenic fungi and oomycetes. The culture filtrate of strain NM4 with the fungicide effectively suppressed the mycelial growth of A. solani, with the highest growth inhibition rate of 83.48%. Although exposure to culture filtrate prompted hyphal alterations in A. solani, including bulging, combining it with the fungicide caused more severe hyphal damage with continuous bulging. Surfactins and fengycins, two lipopeptide groups, were isolated and identified as the main compounds in two fractions using LC-ESI-MS. Although the surfactin-containing fraction failed to inhibit growth, the fengycin-containing fraction, alone and in combination with chlorothalonil, restricted mycelial development, producing severe hyphal deformations with formation of chlamydospores. A pot experiment combining strain NM4, applied as a broth culture, with fungicide, at half the recommended concentration, resulted in a significant reduction in potato early blight severity. Our results indicate the feasibility of an integrated approach for the management of early blight in potato that can reduce fungicide application rates, promoting a healthy ecosystem in agriculture.

Safety assessment of surfactin-producing Bacillus strains and their lipopeptides extracts in vitro and in vivo.

Beneficial Bacillus strains can be administered to livestock as probiotics to improve animal health. Cyclic lipopeptides produced by Bacillus such as surfactins may be responsible for some of the beneficial effects due to their anti-inflammatory and immunomodulatory activity. The aim of the present study was to isolate and evaluate the biocompatibility of native Bacillus spp. strains and their surfactin-like lipopeptides in vitro and in vivo to determine their potential to be used on animals. Biocompatibility of endospore suspensions (108 UFC/mL), and different dilutions (1:10; 1:50; 1:100; 1:500, and 1:1000) of Bacillus lipopeptide extracts containing surfactin was tested on Caco-2 cells by microculture tetrazolium-based colorimetric assay. Genotoxicity was tested on BALB/c mice (n = 6) administered 0.2 mL of endospore suspensions by the bone marrow erythrocyte micronuclei assay. All the isolates tested produced between 26.96 and 239.97 µg mL- 1 of surfactin. The lipopeptide extract (LPE) from isolate MFF1.11 demonstrated significant cytotoxicity in vitro. In contrast, LPE from MFF 2.2; MFF 2.7, TL1.11, TL 2.5, and TC12 had no cytotoxic effect (V% > 70%) on Caco-2 cells, not affecting cell viability signifficantly in most treatments. Similarly, none of the endospore suspensions affected cell viability (V% > 80%). Likewise, endospores did not cause genotoxicity on BALB/c mice. This study was elementary as a first step for a new line of research, since it allowed us to choose the safest isolates to keep working on the search of new potentially probiotic strains destined to production animals to improve their performance and health.

Synthetic Self-Adjuvanted Lipopeptide Vaccines Conferred Protection against Helicobacter pylori Infection.

Helicobacter pylori (H. pylori) colonizes the stomach epithelium of half the world's population and is responsible for various digestive diseases and even stomach cancer. Vaccine-mediated protection against H. pylori infection depends primarily on the specific mucosal and T-cell responses. In this study, the synthetic lipopeptide vaccines, Hp4 (Pam2 Cys modified UreB T-cell epitope) and Hp10 (Pam2 Cys modified CagA T/B cell combined epitope), not only induce the bone marrow derived dendritic cells (BMDCs) maturation by activating a variety of pattern-recognition receptors (PRRs) such as Toll-like receptor (TLR), Nod-like receptor (NLR), and retinoic acid-inducing gene (RIG) I-like receptor (RLR), and but also stimulate BMDCs to secret cytokines that have the potential to modulate T-cell activation and differentiation. Although intranasal immunization with Hp4 or Hp10 elicits robust epitope-specific T-cell responses in mice, only Hp10 confers protection against H. pylori infection, possibly due to the fact that Hp10 also induces substantial specific sIgA response at mucosal sites. Interestingly, Hp4 elevates the protective response against H. pylori infection of Hp10 when administrated in combination, characterized by better protective effect and enhanced specific T-cell and mucosal antibody responses. The results suggest that synthetic lipopeptide vaccines based on the epitopes derived from the protective antigens are promising candidates for protection against H. pylori infection.

Production of biosurfactant by salt-resistant Bacillus in lead-supplemented media: application and toxicity.

A group of biosurfactants are lipopeptides that are produced by some microorganisms, especially Bacillus strains. They are new bioactive agents with anticancer, antibacterial, antifungal, and antiviral activities. Also, they are used in sanitation industries. In this study, a lead-resistant strain of Bacillus halotolerans was isolated for lipopeptide production. This isolate exhibited metal resistance (lead, calcium, chromium, nickel, copper, manganese, and mercury), salt tolerance (12%), and antimicrobial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Saccharomyces cerevisiae. The production of lipopeptide was optimized, concentrated, and then extracted from the polyacrylamide gel in a simple way for the first time. The nature of the purified lipopeptide was determined by FTIR, GC/MS, and HPLC analyses. The purified lipopeptide indicated significant antioxidant properties (90.38% at a concentration of 0.8 mg ml-1). Also, it had anticancer activity by apoptosis (flow cytometry analysis) in MCF-7 cells, while it had no cytotoxicity on HEK-293 normal cells. Therefore, Bacillus halotolerans lipopeptide has the potential to be used as an antioxidant, antimicrobial, or anticancer agent in the medical and food industries.

Postexposure Prophylaxis and Treatment of Bacillus anthracis Infections: A Systematic Review and Meta-analyses of Animal Models, 1947-2019.

BACKGROUND: Anthrax is endemic to many countries, including the United States. The causative agent, Bacillus anthracis, poses a global bioterrorism threat. Without effective antimicrobial postexposure prophylaxis (PEPAbx) and treatment, the mortality of systemic anthrax is high. To inform clinical guidelines for PEPAbx and treatment of B. anthracis infections in humans, we systematically evaluated animal anthrax treatment model studies. METHODS: We searched for survival outcome data in 9 scientific search engines for articles describing antimicrobial PEPAbx or treatment of anthrax in animals in any language through February 2019. We performed meta-analyses of efficacy of antimicrobial PEPAbx and treatment for each drug or drug combination using random-effects models. Pharmacokinetic/pharmacodynamic relationships were developed for 5 antimicrobials with available pharmacokinetic data. Monte Carlo simulations were used to predict unbound drug exposures in humans. RESULTS: We synthesized data from 34 peer-reviewed studies with 3262 animals. For PEPAbx and treatment of infection by susceptible B. anthracis, effective monotherapy can be accomplished with fluoroquinolones, tetracyclines, ß-lactams (including penicillin, amoxicillin-clavulanate, and imipenem-cilastatin), and lipopeptides or glycopeptides. For naturally occurring strains, unbound drug exposures in humans were predicted to adequately cover the minimal inhibitory concentrations (MICs; those required to inhibit the growth of 50% or 90% of organisms [MIC50 or MIC90]) for ciprofloxacin, levofloxacin, and doxycycline for both the PEPAbx and treatment targets. Dalbavancin covered its MIC50 for PEPAbx. CONCLUSIONS: These animal studies show many reviewed antimicrobials are good choices for PEPAbx or treatment of susceptible B. anthracis strains, and some are also promising options for combating resistant strains. Monte Carlo simulations suggest that oral ciprofloxacin, levofloxacin, and doxycycline are particularly robust choices for PEPAbx or treatment.

Lipopeptide surfactin ameliorates the cell uptake of platensimycin and enhances its therapeutic effect on treatment of MRSA skin infection.

OBJECTIVES: The rapid development of drug-resistant bacteria, especially MRSA, poses severe threats to global public health. Adoption of antibiotic adjuvants has proved to be one of the efficient ways to solve such a crisis. Platensimycin and surfactin were comprehensively studied to combat prevalent MRSA skin infection. METHODS: MICs of platensimycin, surfactin or their combinations were determined by resazurin assay, while the corresponding MBCs were determined by chequerboard assay. Growth inhibition curves and biofilm inhibition were determined by OD measurements. Membrane permeability analysis was conducted by propidium iodide staining, and morphological characterizations were performed by scanning electron microscopy. Finally, the therapeutic effects on MRSA skin infections were evaluated in scald-model mice. RESULTS: The in vitro assays indicated that surfactin could significantly improve the antibacterial performance of platensimycin against MRSA, especially the bactericidal activity. Subsequent mechanistic studies revealed that surfactin not only interfered with the biofilm formation of MRSA, but also disturbed their cell membranes to enhance membrane permeability, and therefore synergistically ameliorated MRSA cellular uptake of platensimycin. Further in vivo assessment validated the synergistic effect of surfactin on platensimycin and the resultant enhancement of therapeutical efficacy in MRSA skin-infected mice. CONCLUSIONS: The combination of effective and biosafe surfactin and platensimycin could be a promising and efficient treatment for MRSA skin infection, which could provide a feasible solution to combat the major global health threats caused by MRSA.

Antimicrobial and antioxidant activities of Bacillus mojavensis I4 lipopeptides and their potential application against the potato dry rot causative Fusarium solani.

Lipopeptides are diverse metabolites produced by various bacterial and fungal genera. They are known for their antimicrobial and surfactant activities with diverse environmental, pharmaceutical, and also agronomic applications as biocontrol agents. In this study, a PCR was used to confirm the presence of NRPS genes in Bacillus mojavensis I4. This bacterial strain could produce diverse lipopeptides which belong to the fengycin, and surfactin families. The antioxidant activity of I4 biosurfactants was determined through four different in vitro assays. Furthermore, antimicrobial activity assays indicated that I4 lipopeptides exhibited marked inhibitory activity against several bacterial and fungal strains. Further treatment of potato dry rot causative pathogen Fusarium solani with I4 lipopeptides demonstrated a remarkable reduction in the fungal penetration by almost 80% after 15 days of incubation. The findings suggest that I4 lipopeptide is a potential biocontrol agent during potato tuber storage.

Disease Inhibiting Effect of Strain Bacillus subtilis EG21 and Its Metabolites Against Potato Pathogens Phytophthora infestans and Rhizoctonia solani.

Potato production worldwide is plagued by several disease-causing pathogens that result in crop and economic losses estimated to billions of dollars each year. To this day, synthetic chemical applications remain the most widespread control strategy despite their negative effects on human and environmental health. Therefore, obtainment of superior biocontrol agents or their naturally produced metabolites to replace fungicides or to be integrated into practical pest management strategies has become one of the main targets in modern agriculture. Our main focus in the present study was to elucidate the antagonistic potential of a new strain identified as Bacillus subtilis EG21 against potato pathogens Phytophthora infestans and Rhizoctonia solani using several in vitro screening assays. Microscopic examination of the interaction between EG21 and R. solani showed extended damage in fungal mycelium, while EG21 metabolites displayed strong anti-oomycete and zoosporecidal effect on P. infestans. Mass spectrometry (MS) analysis revealed that EG21 produced antifungal and anti-oomycete cyclic lipopeptides surfactins (C12 to C19). Further characterization of EG21 confirmed its ability to produce siderophores and the extracellular lytic enzymes cellulase, pectinase and chitinase. The antifungal activity of EG21 cell-free culture filtrate (CF) was found to be stable at high-temperature/pressure treatment and extreme pH values and was not affected by proteinase K treatment. Disease-inhibiting effect of EG21 CF against P. infestans and R. solani infection was confirmed using potato leaves and tubers, respectively. Biotechnological applications of using microbial agents and their bioproducts for crop protection hold great promise to develop into effective, environment-friendly and sustainable biocontrol strategies. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Biocontrol Effect of Bacillus subtilis YPS-32 on Potato Common Scab and Its Complete Genome Sequence Analysis.

Potato common scab is caused by Streptomyces, which resides in soil and has become a serious disease in potato planting areas worldwide. In this study, we obtained a Bacillus subtilis YPS-32 strain by natural screening, and atmospheric and room-temperature plasma (ARTP) mutagenesis and field trial results showed that B. subtilis YPS-32 has a control efficacy of 83.70% against potato common scab. The complete genome of B. subtilis YPS-32 was sequenced, and multiple genes related to the synthesis of antibiotics and plant growth promoters were detected. Based on the genomic information for B. subtilis YPS-32, the sfp gene-inactivated (related to the synthesis of secondary metabolites) mutant strain B. subtilis YPS-32Δsfp was constructed. Analysis of crude extract metabolites using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) techniques revealed that strain YPS-32 encodes antagonists, such as surfactin and fengycin, which have antimicrobial effects. This study clarifies the mode of action by which B. subtilis YPS-32 antagonizes Streptomyces scabies and provides a reference for further research on antibacterial genes in the future.

Caspofungin resistance in Candida albicans: genetic factors and synergistic compounds for combination therapies.

Caspofungin and other echinocandins have been used for the treatment of human infections by the opportunistic yeast pathogen, Candida albicans. There has been an increase in infections by non-albicans Candida species such as Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei, and Candida auris in clinical or hospital settings. This is problematic to public health due to the increasing prevalence of echinocandin resistant species/strains. This review will present a summary on various studies that investigated the inhibitory action of caspofungin on 1,3-ß-D-glucan synthesis, on cell wall structure, and biofilm formation of C. albicans. It will highlight some of the issues linked to caspofungin resistance or reduced caspofungin sensitivity in various Candida species and the potential benefits of antimicrobial peptides and other compounds in synergy with caspofungin.

Structure and stability analysis of antibacterial substance produced by selenium enriched Bacillus cereus BC1.

Microorganisms can produce many antibiotics against bacteria and fungi, which have been used as a potential choice of new antibiotics. In this paper, we studied the characteristics of antibacterial substances by Bacillus cereus BC1. The results showed that the acid-precipitated substance played the main role in antibacterial activity, and further characterization indicated that the antibacterial substance might be a lipopeptide substance. Then the antibacterial spectrum suggested that the antibacterial substance had an inhibitory effect on Gram-positive bacteria and fungi, while selenium-riched antibacterial substance of Bacillus cereus BC1 could significantly enhance the inhibition. Then the morphological effects of the antibacterial substance to indicator bacteria were determined. The effects of different treatment methods on the stability of antibacterial substances were studied and the results showed that the antibacterial substance was stable to heat, ultrasonic, and ultraviolet treatment, and their antibacterial activity would not be greatly affected. However, they were sensitive to pepsin. The optimum pH range of antibacterial activity was 3-5. This study may contribute to reusing the fermentation supernatant often discarded in the previous fermentation process. At the same time, the lipopeptide antibacterial substance extracted from the fermentation broth of selenium-enriched Bacillus cereus BC1 can be used in the development of antibiotics and biopesticides, and open up a new way for the control of plant diseases.

The antifungal activity of caspofungin in combination with antifungals or non-antifungals against Candida species in vitro and in clinical therapy.

INTRODUCTION: Candida species have been regarded as global health threats due to their ability to cause invasive infections. It is challenging to treat Candida bloodstream infections, which are associated with high mortality levels. Monotherapy with antifungals is sometimes not effective against severe Candida infections, and combination therapy is needed in clinical practice. AREAS COVERED: This review was undertaken based on data from a PubMed search for English language reports published before March 2021 by using the terms 'caspofungin,' 'Candida species,' 'combination therapy,' 'antifungal effect,' and 'novel antifungal agent.' EXPERT OPINION: Combination therapy is an empirical strategy for treating refractory Candida infections. Caspofungin has been recommended to treat candidaemia. Caspofungin in combination therapy has some applications, while the efficacy of combination therapy in the treatment of refractory Candida infections needs more study, such as randomized controlled trials. In addition, novel compounds or drugs with potential antifungal activities have been examined, and some of them exhibit synergistic interactions with caspofungin. Thus, the antifungal activity of caspofungin in combination with antifungals or non-antifungals against Candida species in vitro and in clinical therapy is summarized.

Serum apolipoprotein A-I potentiates the therapeutic efficacy of lysocin E against Staphylococcus aureus.

Lysocin E is a lipopeptide with antibiotic activity against methicillin-resistant Staphylococcus aureus. For unclear reasons, the antibacterial activity of lysocin E in a mouse systemic infection model is higher than expected from in vitro results, and the in vitro activity is enhanced by addition of bovine serum. Here, we confirm that serum from various species, including humans, increases lysocin E antimicrobial activity, and identify apolipoprotein A-I (ApoA-I) as an enhancing factor. ApoA-I increases the antibacterial activity of lysocin E when added in vitro, and the antibiotic displays reduced activity in ApoA-I gene knockout mice. Binding of ApoA-I to lysocin E is enhanced by lipid II, a cell-wall synthesis precursor found in the bacterial membrane. Thus, the antimicrobial activity of lysocin E is potentiated through interactions with host serum proteins and microbial components.

Antiviral activity by lecithin-induced fengycin lipopeptides as a potent key substrate against Cucumber mosaic virus.

In this study, the effect of different growth substrates on the production of biosurfactants in the PPL strain of Bacillus amyloliquefaciens-a biocontrol agent for diseases affecting pepper and tomato plants-and on the antiviral effect of the PPL strain on Cucumber mosaic virus (CMV)-infected pepper plants was investigated. The multifunctional PPL strain exhibited enhanced growth and increased production of biosurfactants upon lecithin supplementation and consequently exhibited potent anti-CMV activity. The enhanced anti-CMV activity of the lecithin-supplemented PPL culture could be attributed to the antiviral effect as well as to the upregulation of plant defense-related genes. Treatment with pure commercial fengycins elicited a defense response against CMV in pepper plants; this effect was similar to that observed upon treatment with the lecithin-supplemented PPL culture. To the best of our knowledge, this is the first study to report the antiviral activity of lecithin-induced fengycin lipopeptides. These results suggest that the growth substrate affects antimicrobial production by B. amyloliquefaciens PPL, and consequently its antiviral activity.

Discovery, Synthesis, and Optimization of Peptide-Based Antibiotics.

The rise of multidrug resistant bacteria has significantly compromised our supply of antibiotics and poses an alarming medical and economic threat to society. To combat this problem, it is imperative that new antibiotics and treatment modalities be developed, especially those toward which bacteria are less capable of developing resistance. Peptide natural products stand as promising candidates to meet this need as bacterial resistance is typically slow in response to their unique modes of action. They also have additional benefits including favorable modulation of host immune responses and often possess broad-spectrum activity against notoriously treatment resistant bacterial biofilms. Moreover, nature has provided a wealth of peptide-based natural products from a range of sources, including bacteria and fungi, which can be hijacked in order to combat more dangerous clinically relevant infections.This Account highlights recent advances in the total synthesis and development of a range of peptide-based natural product antibiotics and details the medicinal chemistry approaches used to optimize their activity.In the context of antibiotics with potential to treat Gram-positive bacterial infections, this Account covers the synthesis and optimization of the natural products daptomycin, glycocin F, and alamethicin. In particular, the reported synthesis of daptomycin highlights the utility of on-resin ozonolysis for accessing a key kynurenine residue from the canonical amino acid tryptophan. Furthermore, the investigation into glycocin F analogues uncovered a potent lead compound against Lactobacillus plantarum that bears a non-native thioacetal linkage to a N-acetyl-d-glucosamine (GlcNAc) sugar, which is otherwise O-linked in its native form.For mycobacterial infections, this Account covers the synthesis and optimization of teixobactin, callyaerin A, lassomycin, and trichoderin A. The synthesis of callyaerin A, in particular, highlighted the importance of a (Z)-2,3-diaminoacrylamide motif for antimicrobial activity against Mycobacterium tuberculosis, while the synthesis of trichoderin A highlighted the importance of (R)-stereoconfiguration in a key 2-amino-6-hydroxy-4-methyl-8-oxodecanoic acid (AHMOD) residue.Lastly, this Account covers lipopeptide antibiotics bearing activity toward Gram-negative bacterial infections, namely, battacin and paenipeptin C. In both cases, optimization of the N-terminal lipid tails led to the identification of analogues with potent activity toward Escherichia coli and Pseudomonas aeruginosa.

Effect of zinc oxide nanoparticle supplementation on the enhanced production of surfactin and iturin lipopeptides of endophytic Bacillus sp. Fcl1 and its ameliorated antifungal activity.

BACKGROUND: Lipopeptides from the Bacillus spp. possess an excellent spectrum of antimicrobial properties which make them suitable candidates to be explored for the food, agricultural, pharmaceutical and biotechnological applications. As the low yield of the lipopeptides limits their applications, methods to enhance their production are highly significant. RESULTS: In this study, extracts prepared from endophytic Bacillus sp. Fcl1 cultured in the presence of various supplements were screened for antifungal activity against Pythium aphanidermatum. From the results, the supplementation of carbon sources and zinc oxide nanoparticles (ZnONPs) was found to have an enhancement effect on the antifungal activity of Bacillus sp. Fcl1. Among these, the highest antifungal activity (73.2%) could be observed for the Fcl1 sample cultured with 5 mg L-1 of ZnONP supplementation. The growth of Fcl1 in the presence of ZnONPs also indicated its compatibility with the nano-supplement in the concentration range used. By liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) analysis, the synthesis of increased numbers of lipopeptide surfactin derivatives could be identified from the extracts of Fcl1 prepared from the carbon sources and ZnONP-supplemented cultures. In addition to the surfactin derivatives, the presence of another lipopeptide iturin was also detected from the extracts of Fcl1 cultured with ZnONPs. CONCLUSION: ZnONP supplementation was found to enhance antifungal activity and lipopeptide production in the Bacillus sp. Fcl1. The use of nanoparticles to enhance the antifungal mechanisms of Fcl1 as observed in the study provides novel insights to explore its applications for sustainable agricultural productivity.

LPD-12: a promising lipopeptide to control COVID-19.

INTRODUCTION: The recent pandemic outbreak of SARS-CoV-2 has been associated with a lethal atypical pneumonia, making COVID-19 an urgent public health issue with an increasing rate of mortality and morbidity. There are currently no vaccines or therapeutics available for COVID-19, which is causing an urgent search for a new drug to combat the COVID-19 pandemic. The lipid membrane alternation efficiency of small antimicrobial lipopeptides enables them to block viral membrane fusion to the host cell. Lipopeptides could serve as potential antiviral agents, by interacting or competing with viral fusion proteins. METHODS: This study screened seven different lipopeptides (tsushimycin, daptomycin, surfactin, bacillomycin, iturin, srfTE, and LPD-12) and docked them individually against the spike (S)-glycoprotein of SARS-CoV-2. RESULTS: Based on the maximum docked score and minimum atomic contact energy, LPD-12 (-1137.38 kcal) was the appropriate molecule for proper binding with the S-glycoprotein of SARS-CoV-2 and thus significantly interrupted its affinity of binding with angiotensin-converting enzyme-2 (ACE2), which is the only receptor molecule found to be facilitating disease development. The results confirmed a strong binding affinity of LPD-12 with ACE2, with a binding free energy of -1621.62 kcal, which could also reciprocally prevent the binding of S-protein. CONCLUSTION: It can be concluded that LPD-12 may act as a potential therapeutic drug, by reducing the entry of SARS-CoV-2 to the human cells via the ACE2 receptor and related infections.

Antifungal evaluation of fengycin isoforms isolated from Bacillus amyloliquefaciens PPL against Fusarium oxysporum f. sp. lycopersici.

Bacillus amyloliquefaciens PPL is known to have a broad spectrum antifungal activity against plant pathogenic fungi. We focused on the cyclic lipopeptides (CLPs) extracted from the culture broth that are known to promote the ability and the efficiency of B. amyloliquefaciens PPL to control fungal diseases in pepper and tomato. In this study, the PPL strain exhibited enhanced culture yield and increased production of fengycin lipopeptides upon lecithin supplementation. The purified iturin A fraction from strain PPL exhibited higher antifungal activity (73 - 80%) against pepper anthracnose than fengycin fraction in vitro and in vivo. However, the control of tomato Fusarium wilt by the PPL strain was mainly attributed to fengycin lipopeptides. A comparison of liquid chromatography-mass spectrometry (LC-MS) and LC-tandem MS analysis of the filtrate, we found that the antifungal compounds against Fusarium wilt present in the strain PPL culture filtrate were a series of isoforms of fengycin (type F1, F2, and F3). The purified fengycin F1 type showed better antifungal activity against Fusarium wilt compared the other isoforms. To the best of our knowledge, this is the first study to report the antifungal activity of fengycin isoform types in the context of Fusarium wilt. The CLPs produced by the PPL strain are potential candidates for controlling fungal disease in tomato and pepper plants.

Viennamycins: Lipopeptides Produced by a Streptomyces sp.

Extracts from Streptomyces sp. S4.7 isolated from the rhizosphere of edelweiss, an alpine medicinal plant, exhibited activity against Gram-positive bacteria. LC-HRMS analyses of the extracts resulted in the detection of two unknown, structurally related lipopeptides that were assumed to be responsible for the antibiotic activity. LC-MS guided isolation and structure elucidation of viennamycins A and B (1 and 2) by HR-MS/MS, 1D and 2D NMR, and Marfey's analyses revealed them to be novel compounds, with viennamycin A containing cysteic acid, a unique feature for lipopeptides. Tests for antibacterial, antifungal, and cytotoxic activities of purified viennamycins, both with and without divalent cations, did not reveal any bioactivity, suggesting that their biological function, which could not be determined in the tests used, is atypical for lipopeptides. The genome of Streptomyces sp. S4.7 was sequenced and analyzed, revealing the viennamycin biosynthetic gene cluster. Detailed bioinformatics-based analysis of the viennamycin gene cluster allowed elucidation of the biosynthetic pathway for these lipopeptides.

Surfactin and fengycin B extracted from Bacillus pumilus W-7 provide protection against potato late blight via distinct and synergistic mechanisms.

Potato late blight caused by Phytophthora infestans is one of the most serious plant diseases worldwide. Cyclic lipopeptides (CLPs) extracted from Bacillus strains exhibit a promising effect in the biocontrol of a variety of phytopathogens. However, the specific inhibitory effects and underlying mechanisms of CLPs against P. infestans are poorly understood. In this study, we showed that Bacillus pumilus W-7 can inhibit the growth of P. infestans mycelium. Two metabolites from W-7, surfactin and fengycin B, were identified using MS/MS. Fengycin B inhibited mycelium growth by inducing mycelium deformations, oxidative damage, and mitochondrial dysfunction. Surfactin induced potato plant defense responses by increasing the expression of the biocontrol genes (pod, pal, and cat) and their enzyme activities (POD, PAL, and CAT). Also, surfactin and fengycin B could exhibit a synergistic inhibitory effect on P. infestans. Taken together, our findings indicate that B. pumilus W-7 and its CLPs are potential environmentally friendly and effective biocontrol agents for the preservation of potato crops. KEY POINTS: • Lipopeptides of surfactin and fengycin B are extracted from Bacillus pumilus W-7. • Fengycin B inhibits Phytophthora infestans mycelium growth in a direct manner. • Surfactin induces potato plant defense responses to control late blight.